Sleeping 3.5, 6 or 8 hours - what's best?

A six year study of more than one million adults ages 30 to 102 shows that people that sleep only 6 to 7 hours a night have a lower death rate than those who sleep 8 hours a day.

The report also covers the danger of sleeping pills, stating that the risk of taking sleeping pills 30 times or more a month is about the same as the risk of smoking a pack of cigarettes a day:

Those who took sleeping pills nightly had a greater risk of death than those who took them occasionally, but the latter risk was still 10 to 15 percent higher than it was among people who never took sleeping pills.

Sleeping pills appear unsafe in any amount, Kripke writes in his online book, "The Dark Side of Sleeping Pills."

"There is really no evidence that the average 8-hour sleeper functions better than the average 6- or 7-hour sleeper," Kripke says, on the basis of his ongoing psychiatric practice with patients along with research, including the large study of a million adults (called the Cancer Prevention Study II).

Another interesting conclusion is that people that sleep 3.5 hours per night, or have serious insomnia, live longer than people who get more than 7.5 hours sleep per night.